An air pre-heater includes a heat exchange element made of ceramic material. The heat exchanger made of ceramic material has been applied. Such heat exchangers, having an applicable temperature generally up to 1400°, are especially suitable for waste heat recovery from the high-temperature flue gas. Meanwhile, due to the corrosion resistance of the ceramic material, such heat exchangers are also suitable for waste heat recovery from the low-temperature flue gas. The technical status is as shown in the following publications:
U.S. Pat. No. 4,681,157, titled “Crossflow Heat Exchanger”;
U.S. Pat. No. 4,083,400, titled “Heat Recuperative Apparatus Incorporating a Cellular Ceramic Core”;
Chinese Patent ZL201010619070.7, titled “Silicon Carbide Ceramic Heat Exchange Plate and Manufacturing Method Thereof”;
Chinese Utility Model Patent ZL90206446, titled “Heat Transfer Tube Assembly of Ceramic Heat Exchanger”;
Chinese Patent ZL94201435, titled “Ceramic Heat Exchanger”;
Chinese Patent ZL200610017968, titled “Ceramic Heat Exchanger, Ceramic Material and Production Method Thereof”.
U.S. Pat. No. 4,681,157 further provides a crossflow heat exchanger, a heat exchange main body thereof is formed by laying a plurality of cube honeycomb ceramic pieces, and the air tightness of the heat exchange main body is ensured by grooves and flanges on the four sides of the side faces of the cube honeycomb ceramic pieces, sealing strips are arranged between each pair of grooves and flanges, and the contact sides of ceramic heat exchange elements are sealed by grouting. A large number of grouting-sealing joints in this heat exchanger may lead to poor air tightness thereof.
U.S. Pat. No. 4,083,400 provides two honeycomb ceramic cores for a waste heat recovery device. The first honeycomb ceramic core is formed by bonding corrugated ceramic slices and ceramic flat plate spacers with a certain thickness together, and the ceramic spacers are configured to separate flue gas and air. The second honeycomb ceramic core is formed by laminating and bonding the ceramic spacers having fins on one side together. With regard to the first core, the ceramic spacers are likely to generate an internal stress and thus to crack due to the bonding of the corrugated ceramic slices and the ceramic flat plate spacers. With regard to the second core, it may be better. However, for both cores, the volume thereof will not be too large. Because the heat exchanger in this patent is a single-core heat exchanger, it does not involve the connecting and sealing problems of a plurality of honeycomb ceramic cores. It is not suitable for manufacturing multi-core heat exchangers.
Chinese Patent ZL201010619070.7 provides a silicon carbide ceramic heat exchange plate, characterized in that a heat exchange channel of a double-loop structure is arranged on the heat exchange plate, and is an arc-shape or a linear deep groove. This patent does not involve sealing and connection among the plates; and furthermore, the thickness of a single plate and the groove depth are limited. It is not suitable for heat exchange between air and flue gas.
Chinese Patents ZL90206446, ZL94201435, ZL200610017968 provide tube-bundle type ceramic heat exchangers which are formed by combining and laying ceramic heat exchange pipes and various joint disc bricks and refractory bricks; due to the existence of a large number of seams, the gas leakage rate is high, thereby influencing the service life of the heat exchangers.
At present, ceramic tube heat exchangers have been applied to the waste heat recovery from the high-temperature flue gas, but hardly applied to the waste heat recovery from the medium- and low-temperature flue gas. Ceramic plate heat exchangers have been hardly applied to the waste heat recovery from the high-, medium- and low-temperature flue gas.